1. Field of the Invention
The present invention relates generally to an improvement in the structure of a coupling for connecting a resin tube having a relatively small diameter such as 20 mm or less and arranged as an oil or air supply conduit in an automobile or a variety of machines or apparatus.
2. Description of the Prior Art
A coupling in accordance with the prior art is shown in FIGS. 5a and 5b, and includes a cylindrical coupling body 11. The body 11 has a front end with a communication hole 12 extending axially therein. The body 11 further has a rear end with a stepped chamber extending therein and communicating with the hole 12. A disk-shaped grip 15 with pawl walls 15' extending inwardly is retained in the stepped chamber by a retainer 16. The rear end of the coupling body 11 is press-fitted inwardly to hold the retainer in the stepped chamber, and to thereby position the disk-shaped grip 15. Reference numeral 17 designates a release tool for engaging with the circumferential edge of the axial hole and moving back and forth to release the bite of a resin tube P' by the pawl wall 15'.
In this prior art, however, each pawl wall 15' has such a high rigidity that no bending occurs during fitting of the resin tube P', and the outer circumference of the resin tube P' is scratched in the axial direction. Since the fixed construction is positioned in front of the grip 15 and since the seal ring 14 is fitted in the seal groove 11', the gripping at the pawl wall 15' and the sealing effect at the seal ring 14 are deteriorated to invite a problem that a leakage is frequently induced for a long time.